Dinosaur Polo Club’s transport-puzzler Mini Metro has sold over one million copies.

The minimalist puzzle-strategy title launched on PC in late 2015, before hitting mobile platforms a year later. Mini Metro came to Nintendo Switch earlier this year, which likely helped boost sales past the million mark.

On top of the sales figure, Mini Metro will also be added to Mightier, a platform set up by Boston Children’s Hospital. The service aims to help young kids and teens manage intense emotional reactions and cope with stress.

The platform pairs games with a heart rate monitor that increases difficulty with stress levels, encouraging the introduction of calming techniques.

"The work Mightier is doing to improve children's emotional regulation through the power of play is inspiring," said Dinosaur Polo Club co-founder Robert Curry.

"Mini Metro has unexpectedly received praise as a 'game for good' and an 'empathy simulator,' so we're thrilled to see it added to the Mightier library, knowing that our work can help families and society at large."